Spinal anesthesia for cesarean section: comparative study between isobaric and hyperbaric bupivacaine associated to morphine.

Background And Objectives: Bupivacaine preparations, plain or with glucose, are frequently used in the clinical practice. Blockade upper level is determined by local anesthetic spread in the CSF. This study aimed at comparing isobaric and hyperbaric bupivacaine in patients submitted to spinal anesthesia for Cesarean section.

Methods: In this prospective, randomized and double-blind study 60 patients submitted to spinal anesthesia for Cesarean section were distributed in two groups: IB - (0.5% isobaric bupivacaine, 12.5 mg) and HB - (0.5% hyperbaric bupivacaine, 12.5 mg). After monitoring, venous puncture was performed followed by hydration with lactated Ringers solution. Spinal puncture was paramedially performed at L3-L4 interspace with 27G Quincke needle. Following the CSF dripping, morphine (100 microg) and bupivacaine were separately injected at the speed of 1 ml. 15 s(-1). With the patient back to supine position, two parameters were recorded: onset time (absence of sensitivity in L3) at 1-minute intervals as well as motor and sensory block after 20 minutes. All patients were kept with preanesthetic blood pressure levels until umbilical cord clamping, and if necessary, ephedrine was administered. Neonates were evaluated by Apgars score at 1 and 5 minutes. Sensory and motor blocks were also evaluated at PACU 120 minutes after local anesthetic injection.

Results: Groups were homogeneous. Onset time: Group IB (1', 50") and HB (1', 33"), with no statistical difference. Motor and sensory block at twenty minutes showed no significant difference. Ephedrine consumption: IB (11.83 mg) and HB (14.17 mg), showed also no statistical difference. PACU motor block evaluation showed significant differences.

Conclusions: We concluded that 12.5 mg isobaric and hyperbaric bupivacaine associated to morphine (100 microg) in spinal anesthesia for Cesarean section in term pregnant women are effective and present similar profiles.